OpenCover and FitNesse/fitSharp

OpenCover is a great tool for measuring .NET code coverage. In ATDD some tests are written and documented below system level.
If you use FitNesse/fitSharp the code coverage cannot be determined by calling FitNesse on the console via java -jar fitnesse-standalon -c args.

But... the test runner, Runner.exe, is implemented in .NET.

It is called from the FitNesse server with arguments args1 = -r {assembly list} HOST PORT SOCKET.

You can get a coverage report from OpenCover by defining a new test runner using OpenCover as a proxy. The FitNesse server will call the proxy with args1. The new test runner (definable in the wiki via the global variable TEST_RUNNER) will call OpenCover.Console.exe which then calls the original runner passing args1 on and returning its error code with the -returntargetcode argument.